Temperatures in Britain are expected to reach highs of 18C this weekend as forecasters are predicting the warmest temperatures of the year. Photograph: Oli Scarff/Getty Images

It might not yet be time to dust off the barbecues, but the UK is set to enjoy the best weekend of weather so far this year, with near-universal sunshine and temperatures which could edge close to 18C at a peak.

The better of the two days will be tomorrow, according to the Met Office, where high pressure will bring sunshine to virtually all of the country, with just the risk of some cloud on eastern coasts. Temperatures in much of Scotland, Northern Ireland and eastern England are predicted to hit around 14C-15C, while further west and nearer London they will be closer to 17C, or even 18C.

"This is well above the average for this time of year, which is about 11C to 12C," a Met Office spokesman said. "It is only mid-April though, and the clear skies will mean cooler overnight temperatures. There could even be a touch of ground frosts in some rural areas."

Sunday is expected to be similar, but with Northern Ireland and parts of Scotland enjoying the higher temperatures, approaching 17C in some places. Cooler breezes will keep the mercury nearer to 14C-15C in southern England.

"It looks like more of the same for the start of the working week, if a bit cooler, though the north of Scotland could see some heavier cloud," the Met Office spokesman added.

Following its media mauling last year over a press release which incautiously coined the now infamous "barbecue summer" phrase, the Met Office is being careful over longer-range predictions. An online rival sought to benefit last month by issuing its own forecast of sizzling temperatures to come in July and August.